/*
 * Copyright (c) 1997, 2025 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package jakarta.mail.internet;

import jakarta.activation.DataHandler;
import jakarta.activation.DataSource;
import jakarta.activation.FileDataSource;
import jakarta.mail.BodyPart;
import jakarta.mail.EncodingAware;
import jakarta.mail.FolderClosedException;
import jakarta.mail.Header;
import jakarta.mail.IllegalWriteException;
import jakarta.mail.Message;
import jakarta.mail.MessageRemovedException;
import jakarta.mail.MessagingException;
import jakarta.mail.Multipart;
import jakarta.mail.Part;
import jakarta.mail.util.LineOutputStream;
import jakarta.mail.util.StreamProvider.EncoderTypes;

import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;
import java.nio.file.Files;
import java.nio.file.StandardCopyOption;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


/**
 * This class represents a MIME body part. It implements the
 * <code>BodyPart</code> abstract class and the <code>MimePart</code>
 * interface. MimeBodyParts are contained in <code>MimeMultipart</code>
 * objects. <p>
 *
 * MimeBodyPart uses the <code>InternetHeaders</code> class to parse
 * and store the headers of that body part.
 *
 * <hr><strong>A note on RFC 822 and MIME headers</strong><p>
 *
 * RFC 822 header fields <strong>must</strong> contain only
 * US-ASCII characters. MIME allows non ASCII characters to be present
 * in certain portions of certain headers, by encoding those characters.
 * RFC 2047 specifies the rules for doing this. The MimeUtility
 * class provided in this package can be used to to achieve this.
 * Callers of the <code>setHeader</code>, <code>addHeader</code>, and
 * <code>addHeaderLine</code> methods are responsible for enforcing
 * the MIME requirements for the specified headers.  In addition, these
 * header fields must be folded (wrapped) before being sent if they
 * exceed the line length limitation for the transport (1000 bytes for
 * SMTP).  Received headers may have been folded.  The application is
 * responsible for folding and unfolding headers as appropriate.
 *
 * @author John Mani
 * @author Bill Shannon
 * @author Kanwar Oberoi
 * @see jakarta.mail.Part
 * @see jakarta.mail.internet.MimePart
 * @see jakarta.mail.internet.MimeUtility
 */

public class MimeBodyPart extends BodyPart implements MimePart {

    // Paranoia:
    // allow this last minute change to be disabled if it causes problems
    private static final boolean setDefaultTextCharset =
            MimeUtility.getBooleanSystemProperty(
                    "mail.mime.setdefaulttextcharset", true);

    private static final boolean setContentTypeFileName =
            MimeUtility.getBooleanSystemProperty(
                    "mail.mime.setcontenttypefilename", true);

    private static final boolean encodeFileName =
            MimeUtility.getBooleanSystemProperty("mail.mime.encodefilename", false);
    private static final boolean decodeFileName =
            MimeUtility.getBooleanSystemProperty("mail.mime.decodefilename", false);
    private static final boolean ignoreMultipartEncoding =
            MimeUtility.getBooleanSystemProperty(
                    "mail.mime.ignoremultipartencoding", true);
    private static final boolean allowutf8 =
            MimeUtility.getBooleanSystemProperty("mail.mime.allowutf8", true);

    // Paranoia:
    // allow this last minute change to be disabled if it causes problems
    static final boolean cacheMultipart =    // accessed by MimeMessage
            MimeUtility.getBooleanSystemProperty("mail.mime.cachemultipart", true);


    /**
     * The DataHandler object representing this Part's content.
     */
    protected DataHandler dh;

    /**
     * Byte array that holds the bytes of the content of this Part.
     */
    protected byte[] content;

    /**
     * If the data for this body part was supplied by an
     * InputStream that implements the SharedInputStream interface,
     * <code>contentStream</code> is another such stream representing
     * the content of this body part.  In this case, <code>content</code>
     * will be null.
     *
     * @since JavaMail 1.2
     */
    protected InputStream contentStream;

    /**
     * The InternetHeaders object that stores all the headers
     * of this body part.
     */
    protected InternetHeaders headers;

    /**
     * If our content is a Multipart of Message object, we save it
     * the first time it's created by parsing a stream so that changes
     * to the contained objects will not be lost.
     *
     * If this field is not null, it's return by the {@link #getContent}
     * method.  The {@link #getContent} method sets this field if it
     * would return a Multipart or MimeMessage object.  This field is
     * is cleared by the {@link #setDataHandler} method.
     *
     * @since JavaMail 1.5
     */
    protected Object cachedContent;

    /**
     * An empty MimeBodyPart object is created.
     * This body part maybe filled in by a client constructing a multipart
     * message.
     */
    public MimeBodyPart() {
        super();
        headers = new InternetHeaders();
    }

    /**
     * Constructs a MimeBodyPart by reading and parsing the data from
     * the specified input stream. The parser consumes data till the end
     * of the given input stream.  The input stream must start at the
     * beginning of a valid MIME body part and must terminate at the end
     * of that body part. <p>
     *
     * Note that the "boundary" string that delimits body parts must
     * <strong>not</strong> be included in the input stream. The intention
     * is that the MimeMultipart parser will extract each body part's bytes
     * from a multipart stream and feed them into this constructor, without
     * the delimiter strings.
     *
     * @param is the body part Input Stream
     * @throws MessagingException for failures
     */
    public MimeBodyPart(InputStream is) throws MessagingException {
        if (!(is instanceof ByteArrayInputStream) &&
                !(is instanceof BufferedInputStream) &&
                !(is instanceof SharedInputStream))
            is = new BufferedInputStream(is);

        headers = new InternetHeaders(is);

        if (is instanceof SharedInputStream) {
            SharedInputStream sis = (SharedInputStream) is;
            contentStream = sis.newStream(sis.getPosition(), -1);
        } else {
            try {
                content = MimeUtility.getBytes(is);
            } catch (IOException ioex) {
                throw new MessagingException("Error reading input stream", ioex);
            }
        }

    }

    /**
     * Constructs a MimeBodyPart using the given header and
     * content bytes. <p>
     *
     * Used by providers.
     *
     * @param headers The header of this part
     * @param content bytes representing the body of this part.
     * @throws MessagingException for failures
     */
    public MimeBodyPart(InternetHeaders headers, byte[] content)
            throws MessagingException {
        super();
        this.headers = headers;
        this.content = content;
    }

    /**
     * Return the size of the content of this body part in bytes.
     * Return -1 if the size cannot be determined. <p>
     *
     * Note that this number may not be an exact measure of the
     * content size and may or may not account for any transfer
     * encoding of the content. <p>
     *
     * This implementation returns the size of the <code>content</code>
     * array (if not null), or, if <code>contentStream</code> is not
     * null, and the <code>available</code> method returns a positive
     * number, it returns that number as the size.  Otherwise, it returns
     * -1.
     *
     * @return size in bytes, or -1 if not known
     */
    @Override
    public int getSize() throws MessagingException {
        if (content != null)
            return content.length;
        if (contentStream != null) {
            try {
                int size = contentStream.available();
                // only believe the size if it's greate than zero, since zero
                // is the default returned by the InputStream class itself
                if (size > 0)
                    return size;
            } catch (IOException ex) {
                // ignore it
            }
        }
        return -1;
    }

    /**
     * Return the number of lines for the content of this Part.
     * Return -1 if this number cannot be determined. <p>
     *
     * Note that this number may not be an exact measure of the
     * content length and may or may not account for any transfer
     * encoding of the content. <p>
     *
     * This implementation returns -1.
     *
     * @return number of lines, or -1 if not known
     */
    @Override
    public int getLineCount() throws MessagingException {
        return -1;
    }

    /**
     * Returns the value of the RFC 822 "Content-Type" header field.
     * This represents the content type of the content of this
     * body part. This value must not be null. If this field is
     * unavailable, "text/plain" should be returned. <p>
     *
     * This implementation uses <code>getHeader(name)</code>
     * to obtain the requisite header field.
     *
     * @return Content-Type of this body part
     */
    @Override
    public String getContentType() throws MessagingException {
        String s = getHeader("Content-Type", null);
        s = MimeUtil.cleanContentType(this, s);
        if (s == null)
            s = "text/plain";
        return s;
    }

    /**
     * Is this Part of the specified MIME type?  This method
     * compares <strong>only the <code>primaryType</code> and
     * <code>subType</code></strong>.
     * The parameters of the content types are ignored. <p>
     *
     * For example, this method will return <code>true</code> when
     * comparing a Part of content type <strong>"text/plain"</strong>
     * with <strong>"text/plain; charset=foobar"</strong>. <p>
     *
     * If the <code>subType</code> of <code>mimeType</code> is the
     * special character '*', then the subtype is ignored during the
     * comparison.
     *
     * @throws MessagingException for failures
     */
    @Override
    public boolean isMimeType(String mimeType) throws MessagingException {
        return isMimeType(this, mimeType);
    }

    /**
     * Returns the disposition from the "Content-Disposition" header field.
     * This represents the disposition of this part. The disposition
     * describes how the part should be presented to the user. <p>
     *
     * If the Content-Disposition field is unavailable,
     * null is returned. <p>
     *
     * This implementation uses <code>getHeader(name)</code>
     * to obtain the requisite header field.
     *
     * @throws MessagingException for failures
     * @see #headers
     */
    @Override
    public String getDisposition() throws MessagingException {
        return getDisposition(this);
    }

    /**
     * Set the disposition in the "Content-Disposition" header field
     * of this body part.  If the disposition is null, any existing
     * "Content-Disposition" header field is removed.
     *
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     * @throws MessagingException    for other failures
     */
    @Override
    public void setDisposition(String disposition) throws MessagingException {
        setDisposition(this, disposition);
    }

    /**
     * Returns the content transfer encoding from the
     * "Content-Transfer-Encoding" header
     * field. Returns <code>null</code> if the header is unavailable
     * or its value is absent. <p>
     *
     * This implementation uses <code>getHeader(name)</code>
     * to obtain the requisite header field.
     *
     * @see #headers
     */
    @Override
    public String getEncoding() throws MessagingException {
        return getEncoding(this);
    }

    /**
     * Returns the value of the "Content-ID" header field. Returns
     * <code>null</code> if the field is unavailable or its value is
     * absent. <p>
     *
     * This implementation uses <code>getHeader(name)</code>
     * to obtain the requisite header field.
     */
    @Override
    public String getContentID() throws MessagingException {
        return getHeader("Content-Id", null);
    }

    /**
     * Set the "Content-ID" header field of this body part.
     * If the <code>cid</code> parameter is null, any existing
     * "Content-ID" is removed.
     *
     * @param cid the Content-ID
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     * @throws MessagingException    for other failures
     * @since JavaMail 1.3
     */
    public void setContentID(String cid) throws MessagingException {
        if (cid == null)
            removeHeader("Content-ID");
        else
            setHeader("Content-ID", cid);
    }

    /**
     * Return the value of the "Content-MD5" header field. Returns
     * <code>null</code> if this field is unavailable or its value
     * is absent. <p>
     *
     * This implementation uses <code>getHeader(name)</code>
     * to obtain the requisite header field.
     */
    @Override
    public String getContentMD5() throws MessagingException {
        return getHeader("Content-MD5", null);
    }

    /**
     * Set the "Content-MD5" header field of this body part.
     *
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     */
    @Override
    public void setContentMD5(String md5) throws MessagingException {
        setHeader("Content-MD5", md5);
    }

    /**
     * Get the languages specified in the Content-Language header
     * of this MimePart. The Content-Language header is defined by
     * RFC 1766. Returns <code>null</code> if this header is not
     * available or its value is absent. <p>
     *
     * This implementation uses <code>getHeader(name)</code>
     * to obtain the requisite header field.
     */
    @Override
    public String[] getContentLanguage() throws MessagingException {
        return getContentLanguage(this);
    }

    /**
     * Set the Content-Language header of this MimePart. The
     * Content-Language header is defined by RFC 1766.
     *
     * @param languages array of language tags
     */
    @Override
    public void setContentLanguage(String[] languages)
            throws MessagingException {
        setContentLanguage(this, languages);
    }

    /**
     * Returns the "Content-Description" header field of this body part.
     * This typically associates some descriptive information with
     * this part. Returns null if this field is unavailable or its
     * value is absent. <p>
     *
     * If the Content-Description field is encoded as per RFC 2047,
     * it is decoded and converted into Unicode. If the decoding or
     * conversion fails, the raw data is returned as is. <p>
     *
     * This implementation uses <code>getHeader(name)</code>
     * to obtain the requisite header field.
     *
     * @return content description
     */
    @Override
    public String getDescription() throws MessagingException {
        return getDescription(this);
    }

    /**
     * Set the "Content-Description" header field for this body part.
     * If the description parameter is <code>null</code>, then any
     * existing "Content-Description" fields are removed. <p>
     *
     * If the description contains non US-ASCII characters, it will
     * be encoded using the platform's default charset. If the
     * description contains only US-ASCII characters, no encoding
     * is done and it is used as is. <p>
     *
     * Note that if the charset encoding process fails, a
     * MessagingException is thrown, and an UnsupportedEncodingException
     * is included in the chain of nested exceptions within the
     * MessagingException.
     *
     * @param description content description
     * @throws MessagingException    otherwise; an
     *                                  UnsupportedEncodingException may be included
     *                                  in the exception chain if the charset
     *                                  conversion fails.
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     */
    @Override
    public void setDescription(String description) throws MessagingException {
        setDescription(description, null);
    }

    /**
     * Set the "Content-Description" header field for this body part.
     * If the description parameter is <code>null</code>, then any
     * existing "Content-Description" fields are removed. <p>
     *
     * If the description contains non US-ASCII characters, it will
     * be encoded using the specified charset. If the description
     * contains only US-ASCII characters, no encoding  is done and
     * it is used as is. <p>
     *
     * Note that if the charset encoding process fails, a
     * MessagingException is thrown, and an UnsupportedEncodingException
     * is included in the chain of nested exceptions within the
     * MessagingException.
     *
     * @param description Description
     * @param charset     Charset for encoding
     * @throws MessagingException    otherwise; an
     *                                  UnsupportedEncodingException may be included
     *                                  in the exception chain if the charset
     *                                  conversion fails.
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     */
    public void setDescription(String description, String charset)
            throws MessagingException {
        setDescription(this, description, charset);
    }

    /**
     * Get the filename associated with this body part. <p>
     *
     * Returns the value of the "filename" parameter from the
     * "Content-Disposition" header field of this body part. If its
     * not available, returns the value of the "name" parameter from
     * the "Content-Type" header field of this body part.
     * Returns <code>null</code> if both are absent. <p>
     *
     * If the <code>mail.mime.decodefilename</code> System property
     * is set to true, the {@link MimeUtility#decodeText
     * MimeUtility.decodeText} method will be used to decode the
     * filename.  While such encoding is not supported by the MIME
     * spec, many mailers use this technique to support non-ASCII
     * characters in filenames.  The default value of this property
     * is false.
     *
     * @return filename
     */
    @Override
    public String getFileName() throws MessagingException {
        return getFileName(this);
    }

    /**
     * Set the filename associated with this body part, if possible. <p>
     *
     * Sets the "filename" parameter of the "Content-Disposition"
     * header field of this body part.  For compatibility with older
     * mailers, the "name" parameter of the "Content-Type" header is
     * also set. <p>
     *
     * If the <code>mail.mime.encodefilename</code> System property
     * is set to true, the {@link MimeUtility#encodeText
     * MimeUtility.encodeText} method will be used to encode the
     * filename.  While such encoding is not supported by the MIME
     * spec, many mailers use this technique to support non-ASCII
     * characters in filenames.  The default value of this property
     * is false.
     *
     * @param filename the file name
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     * @throws MessagingException    for other failures
     */
    @Override
    public void setFileName(String filename) throws MessagingException {
        setFileName(this, filename);
    }

    /**
     * Return a decoded input stream for this body part's "content". <p>
     *
     * This implementation obtains the input stream from the DataHandler.
     * That is, it invokes getDataHandler().getInputStream();
     *
     * @return an InputStream
     * @throws IOException        this is typically thrown by the
     *                               DataHandler. Refer to the documentation for
     *                               jakarta.activation.DataHandler for more details.
     * @throws MessagingException for other failures
     * @see #getContentStream
     * @see jakarta.activation.DataHandler#getInputStream
     */
    @Override
    public InputStream getInputStream()
            throws IOException, MessagingException {
        return getDataHandler().getInputStream();
    }

    /**
     * Produce the raw bytes of the content. This method is used
     * when creating a DataHandler object for the content. Subclasses
     * that can provide a separate input stream for just the Part
     * content might want to override this method.
     *
     * @return an InputStream containing the raw bytes
     * @throws MessagingException for failures
     * @see #content
     * @see MimeMessage#getContentStream
     */
    protected InputStream getContentStream() throws MessagingException {
        if (contentStream != null)
            return ((SharedInputStream) contentStream).newStream(0, -1);
        if (content != null)
            return new ByteArrayInputStream(content);

        throw new MessagingException("No MimeBodyPart content");
    }

    /**
     * Return an InputStream to the raw data with any Content-Transfer-Encoding
     * intact.  This method is useful if the "Content-Transfer-Encoding"
     * header is incorrect or corrupt, which would prevent the
     * <code>getInputStream</code> method or <code>getContent</code> method
     * from returning the correct data.  In such a case the application may
     * use this method and attempt to decode the raw data itself. <p>
     *
     * This implementation simply calls the <code>getContentStream</code>
     * method.
     *
     * @return an InputStream containing the raw bytes
     * @throws MessagingException for failures
     * @see #getInputStream
     * @see #getContentStream
     * @since JavaMail 1.2
     */
    public InputStream getRawInputStream() throws MessagingException {
        return getContentStream();
    }

    /**
     * Return a DataHandler for this body part's content. <p>
     *
     * The implementation provided here works just like the
     * the implementation in MimeMessage.
     *
     * @see MimeMessage#getDataHandler
     */
    @Override
    public DataHandler getDataHandler() throws MessagingException {
        if (dh == null)
            dh = new MimePartDataHandler(this);
        return dh;
    }

    /**
     * Return the content as a Java object. The type of the object
     * returned is of course dependent on the content itself. For
     * example, the native format of a text/plain content is usually
     * a String object. The native format for a "multipart"
     * content is always a Multipart subclass. For content types that are
     * unknown to the DataHandler system, an input stream is returned
     * as the content. <p>
     *
     * This implementation obtains the content from the DataHandler.
     * That is, it invokes getDataHandler().getContent();
     * If the content is a Multipart or Message object and was created by
     * parsing a stream, the object is cached and returned in subsequent
     * calls so that modifications to the content will not be lost.
     *
     * @return Object
     * @throws IOException        this is typically thrown by the
     *                               DataHandler. Refer to the documentation for
     *                               jakarta.activation.DataHandler for more details.
     * @throws MessagingException for other failures
     */
    @Override
    public Object getContent() throws IOException, MessagingException {
        if (cachedContent != null)
            return cachedContent;
        Object c;
        try {
            c = getDataHandler().getContent();
        } catch (IOException e) {
            if (e.getCause() instanceof FolderClosedException) {
                FolderClosedException fce = (FolderClosedException) e.getCause();
                throw new FolderClosedException(fce.getFolder(), e.getMessage());
            } else if (e.getCause() instanceof MessagingException) {
                throw new MessageRemovedException(e.getMessage());
            } else {
                throw e;
            }
        }
        if (cacheMultipart &&
                (c instanceof Multipart || c instanceof Message) &&
                (content != null || contentStream != null)) {
            cachedContent = c;
            /*
             * We may abandon the input stream so make sure
             * the MimeMultipart has consumed the stream.
             */
            if (c instanceof MimeMultipart)
                ((MimeMultipart) c).parse();
        }
        return c;
    }

    /**
     * This method provides the mechanism to set this body part's content.
     * The given DataHandler object should wrap the actual content.
     *
     * @param dh The DataHandler for the content
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     */
    @Override
    public void setDataHandler(DataHandler dh)
            throws MessagingException {
        this.dh = dh;
        cachedContent = null;
        MimeBodyPart.invalidateContentHeaders(this);
    }

    /**
     * A convenience method for setting this body part's content. <p>
     *
     * The content is wrapped in a DataHandler object. Note that a
     * DataContentHandler class for the specified type should be
     * available to the Jakarta Mail implementation for this to work right.
     * That is, to do <code>setContent(foobar, "application/x-foobar")</code>,
     * a DataContentHandler for "application/x-foobar" should be installed.
     * Refer to the Java Activation Framework for more information.
     *
     * @param o    the content object
     * @param type Mime type of the object
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification of
     *                                  existing values
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     */
    @Override
    public void setContent(Object o, String type)
            throws MessagingException {
        if (o instanceof Multipart) {
            setContent((Multipart) o);
        } else {
            setDataHandler(new DataHandler(o, type));
        }
    }

    /**
     * Convenience method that sets the given String as this
     * part's content, with a MIME type of "text/plain". If the
     * string contains non US-ASCII characters, it will be encoded
     * using the platform's default charset. The charset is also
     * used to set the "charset" parameter. <p>
     *
     * Note that there may be a performance penalty if
     * <code>text</code> is large, since this method may have
     * to scan all the characters to determine what charset to
     * use. <p>
     *
     * If the charset is already known, use the
     * <code>setText</code> method that takes the charset parameter.
     *
     * @param text the text content to set
     * @throws MessagingException if an error occurs
     * @see #setText(String text, String charset)
     */
    @Override
    public void setText(String text) throws MessagingException {
        setText(text, null);
    }

    /**
     * Convenience method that sets the given String as this part's
     * content, with a MIME type of "text/plain" and the specified
     * charset. The given Unicode string will be charset-encoded
     * using the specified charset. The charset is also used to set
     * the "charset" parameter.
     *
     * @param text    the text content to set
     * @param charset the charset to use for the text
     * @throws MessagingException if an error occurs
     */
    @Override
    public void setText(String text, String charset)
            throws MessagingException {
        setText(this, text, charset, "plain");
    }

    /**
     * Convenience method that sets the given String as this part's
     * content, with a primary MIME type of "text" and the specified
     * MIME subtype.  The given Unicode string will be charset-encoded
     * using the specified charset. The charset is also used to set
     * the "charset" parameter.
     *
     * @param text    the text content to set
     * @param charset the charset to use for the text
     * @param subtype the MIME subtype to use (e.g., "html")
     * @throws MessagingException if an error occurs
     * @since JavaMail 1.4
     */
    @Override
    public void setText(String text, String charset, String subtype)
            throws MessagingException {
        setText(this, text, charset, subtype);
    }

    /**
     * This method sets the body part's content to a Multipart object.
     *
     * @param mp The multipart object that is the Message's content
     * @throws IllegalWriteException if the underlying
     *                                  implementation does not support modification of
     *                                  existing values.
     * @throws IllegalStateException if this body part is
     *                                  obtained from a READ_ONLY folder.
     */
    @Override
    public void setContent(Multipart mp) throws MessagingException {
        setDataHandler(new DataHandler(mp, mp.getContentType()));
        mp.setParent(this);
    }

    /**
     * Use the specified file to provide the data for this part.
     * The simple file name is used as the file name for this
     * part and the data in the file is used as the data for this
     * part.  The encoding will be chosen appropriately for the
     * file data.  The disposition of this part is set to
     * {@link Part#ATTACHMENT Part.ATTACHMENT}.
     *
     * @param file the File object to attach
     * @throws IOException        errors related to accessing the file
     * @throws MessagingException message related errors
     * @since JavaMail 1.4
     */
    public void attachFile(File file) throws IOException, MessagingException {
        FileDataSource fds = new FileDataSource(file);
        this.setDataHandler(new DataHandler(fds));
        this.setFileName(fds.getName());
        this.setDisposition(ATTACHMENT);
    }

    /**
     * Use the specified file to provide the data for this part.
     * The simple file name is used as the file name for this
     * part and the data in the file is used as the data for this
     * part.  The encoding will be chosen appropriately for the
     * file data.
     *
     * @param file the name of the file to attach
     * @throws IOException        errors related to accessing the file
     * @throws MessagingException message related errors
     * @since JavaMail 1.4
     */
    public void attachFile(String file) throws IOException, MessagingException {
        File f = new File(file);
        attachFile(f);
    }

    /**
     * Use the specified file with the specified Content-Type and
     * Content-Transfer-Encoding to provide the data for this part.
     * If contentType or encoding are null, appropriate values will
     * be chosen.
     * The simple file name is used as the file name for this
     * part and the data in the file is used as the data for this
     * part.  The disposition of this part is set to
     * {@link Part#ATTACHMENT Part.ATTACHMENT}.
     *
     * @param file        the File object to attach
     * @param contentType the Content-Type, or null
     * @param encoding    the Content-Transfer-Encoding, or null
     * @throws IOException        errors related to accessing the file
     * @throws MessagingException message related errors
     * @since JavaMail 1.5
     */
    public void attachFile(File file, String contentType, String encoding)
            throws IOException, MessagingException {
        DataSource fds = new EncodedFileDataSource(file, contentType, encoding);
        this.setDataHandler(new DataHandler(fds));
        this.setFileName(fds.getName());
        this.setDisposition(ATTACHMENT);
    }

    /**
     * Use the specified file with the specified Content-Type and
     * Content-Transfer-Encoding to provide the data for this part.
     * If contentType or encoding are null, appropriate values will
     * be chosen.
     * The simple file name is used as the file name for this
     * part and the data in the file is used as the data for this
     * part.  The disposition of this part is set to
     * {@link Part#ATTACHMENT Part.ATTACHMENT}.
     *
     * @param file        the name of the file
     * @param contentType the Content-Type, or null
     * @param encoding    the Content-Transfer-Encoding, or null
     * @throws IOException        errors related to accessing the file
     * @throws MessagingException message related errors
     * @since JavaMail 1.5
     */
    public void attachFile(String file, String contentType, String encoding)
            throws IOException, MessagingException {
        attachFile(new File(file), contentType, encoding);
    }

    /**
     * A FileDataSource class that allows us to specify the
     * Content-Type and Content-Transfer-Encoding.
     */
    private static class EncodedFileDataSource extends FileDataSource
            implements EncodingAware {
        private String contentType;
        private String encoding;

        public EncodedFileDataSource(File file, String contentType,
                                     String encoding) {
            super(file);
            this.contentType = contentType;
            this.encoding = encoding;
        }

        // overrides DataSource.getContentType()
        @Override
        public String getContentType() {
            return contentType != null ? contentType : super.getContentType();
        }

        // implements EncodingAware.getEncoding()
        @Override
        public String getEncoding() {
            return encoding;
        }
    }

    /**
     * Save the contents of this part in the specified file.  The content
     * is decoded and saved, without any of the MIME headers.
     *
     * @param file the File object to write to
     * @throws IOException        errors related to accessing the file
     * @throws MessagingException message related errors
     * @since JavaMail 1.4
     */
    public void saveFile(File file) throws IOException, MessagingException {
        Files.copy(getInputStream(), file.toPath(), StandardCopyOption.REPLACE_EXISTING);
    }

    /**
     * Save the contents of this part in the specified file.  The content
     * is decoded and saved, without any of the MIME headers.
     *
     * @param file the name of the file to write to
     * @throws IOException        errors related to accessing the file
     * @throws MessagingException message related errors
     * @since JavaMail 1.4
     */
    public void saveFile(String file) throws IOException, MessagingException {
        File f = new File(file);
        saveFile(f);
    }

    /**
     * Output the body part as an RFC 822 format stream.
     *
     * @throws IOException        if an error occurs writing to the
     *                               stream or if an error is generated
     *                               by the jakarta.activation layer.
     * @throws MessagingException for other failures
     * @see jakarta.activation.DataHandler#writeTo
     */
    @Override
    public void writeTo(OutputStream os)
            throws IOException, MessagingException {
        writeTo(this, os, null);
    }

    /**
     * Get all the headers for this header_name. Note that certain
     * headers may be encoded as per RFC 2047 if they contain
     * non US-ASCII characters and these should be decoded.
     *
     * @param name name of header
     * @return array of headers
     * @see jakarta.mail.internet.MimeUtility
     */
    @Override
    public String[] getHeader(String name) throws MessagingException {
        return headers.getHeader(name);
    }

    /**
     * Get all the headers for this header name, returned as a single
     * String, with headers separated by the delimiter. If the
     * delimiter is <code>null</code>, only the first header is
     * returned.
     *
     * @param name      the name of this header
     * @param delimiter delimiter between fields in returned string
     * @return the value fields for all headers with
     * this name
     * @throws MessagingException for failures
     */
    @Override
    public String getHeader(String name, String delimiter)
            throws MessagingException {
        return headers.getHeader(name, delimiter);
    }

    /**
     * Set the value for this header_name. Replaces all existing
     * header values with this new value. Note that RFC 822 headers
     * must contain only US-ASCII characters, so a header that
     * contains non US-ASCII characters must be encoded as per the
     * rules of RFC 2047.
     *
     * @param name  header name
     * @param value header value
     * @see jakarta.mail.internet.MimeUtility
     */
    @Override
    public void setHeader(String name, String value)
            throws MessagingException {
        headers.setHeader(name, value);
    }

    /**
     * Add this value to the existing values for this header_name.
     * Note that RFC 822 headers must contain only US-ASCII
     * characters, so a header that contains non US-ASCII characters
     * must be encoded as per the rules of RFC 2047.
     *
     * @param name  header name
     * @param value header value
     * @see jakarta.mail.internet.MimeUtility
     */
    @Override
    public void addHeader(String name, String value)
            throws MessagingException {
        headers.addHeader(name, value);
    }

    /**
     * Remove all headers with this name.
     */
    @Override
    public void removeHeader(String name) throws MessagingException {
        headers.removeHeader(name);
    }

    /**
     * Return all the headers from this Message as an Enumeration of
     * Header objects.
     */
    @Override
    public Enumeration<Header> getAllHeaders() throws MessagingException {
        return headers.getAllHeaders();
    }

    /**
     * Return matching headers from this Message as an Enumeration of
     * Header objects.
     */
    @Override
    public Enumeration<Header> getMatchingHeaders(String[] names)
            throws MessagingException {
        return headers.getMatchingHeaders(names);
    }

    /**
     * Return non-matching headers from this Message as an
     * Enumeration of Header objects.
     */
    @Override
    public Enumeration<Header> getNonMatchingHeaders(String[] names)
            throws MessagingException {
        return headers.getNonMatchingHeaders(names);
    }

    /**
     * Add a header line to this body part
     */
    @Override
    public void addHeaderLine(String line) throws MessagingException {
        headers.addHeaderLine(line);
    }

    /**
     * Get all header lines as an Enumeration of Strings. A Header
     * line is a raw RFC 822 header line, containing both the "name"
     * and "value" field.
     */
    @Override
    public Enumeration<String> getAllHeaderLines() throws MessagingException {
        return headers.getAllHeaderLines();
    }

    /**
     * Get matching header lines as an Enumeration of Strings.
     * A Header line is a raw RFC 822 header line, containing both
     * the "name" and "value" field.
     */
    @Override
    public Enumeration<String> getMatchingHeaderLines(String[] names)
            throws MessagingException {
        return headers.getMatchingHeaderLines(names);
    }

    /**
     * Get non-matching header lines as an Enumeration of Strings.
     * A Header line is a raw RFC 822 header line, containing both
     * the "name"  and "value" field.
     */
    @Override
    public Enumeration<String> getNonMatchingHeaderLines(String[] names)
            throws MessagingException {
        return headers.getNonMatchingHeaderLines(names);
    }

    /**
     * Examine the content of this body part and update the appropriate
     * MIME headers.  Typical headers that get set here are
     * <code>Content-Type</code> and <code>Content-Transfer-Encoding</code>.
     * Headers might need to be updated in two cases:
     *
     * <br>
     * - A message being crafted by a mail application will certainly
     * need to activate this method at some point to fill up its internal
     * headers.
     *
     * <br>
     * - A message read in from a Store will have obtained
     * all its headers from the store, and so doesn't need this.
     * However, if this message is editable and if any edits have
     * been made to either the content or message structure, we might
     * need to resync our headers.
     *
     * <br>
     * In both cases this method is typically called by the
     * <code>Message.saveChanges</code> method. <p>
     *
     * If the {@link #cachedContent} field is not null (that is,
     * it references a Multipart or Message object), then
     * that object is used to set a new DataHandler, any
     * stream data used to create this object is discarded,
     * and the {@link #cachedContent} field is cleared.
     *
     * @throws MessagingException for failures
     */
    protected void updateHeaders() throws MessagingException {
        updateHeaders(this);
        /*
         * If we've cached a Multipart or Message object then
         * we're now committed to using this instance of the
         * object and we discard any stream data used to create
         * this object.
         */
        if (cachedContent != null) {
            dh = new DataHandler(cachedContent, getContentType());
            cachedContent = null;
            content = null;
            if (contentStream != null) {
                try {
                    contentStream.close();
                } catch (IOException ioex) {
                }    // nothing to do
            }
            contentStream = null;
        }
    }

    /////////////////////////////////////////////////////////////
    // Package private convenience methods to share code among //
    // MimeMessage and MimeBodyPart                            //
    /////////////////////////////////////////////////////////////

    static boolean isMimeType(MimePart part, String mimeType)
            throws MessagingException {
        // XXX - lots of room for optimization here!
        String type = part.getContentType();
        try {
            return new ContentType(type).match(mimeType);
        } catch (ParseException ex) {
            // we only need the type and subtype so throw away the rest
            try {
                int i = type.indexOf(';');
                if (i > 0)
                    return new ContentType(type.substring(0, i)).match(mimeType);
            } catch (ParseException pex2) {
            }
            return type.equalsIgnoreCase(mimeType);
        }
    }

    static void setText(MimePart part, String text, String charset,
                        String subtype) throws MessagingException {
        if (charset == null) {
            if (MimeUtility.checkAscii(text) != MimeUtility.ALL_ASCII)
                charset = MimeUtility.getDefaultMIMECharset();
            else
                charset = "us-ascii";
        }
        // XXX - should at least ensure that subtype is an atom
        part.setContent(text, "text/" + subtype + "; charset=" +
                MimeUtility.quote(charset, HeaderTokenizer.MIME));
    }

    static String getDisposition(MimePart part) throws MessagingException {
        String s = part.getHeader("Content-Disposition", null);

        if (s == null)
            return null;

        ContentDisposition cd = new ContentDisposition(s);
        return cd.getDisposition();
    }

    static void setDisposition(MimePart part, String disposition)
            throws MessagingException {
        if (disposition == null)
            part.removeHeader("Content-Disposition");
        else {
            String s = part.getHeader("Content-Disposition", null);
            if (s != null) {
                /* A Content-Disposition header already exists ..
                 *
                 * Override disposition, but attempt to retain
                 * existing disposition parameters
                 */
                ContentDisposition cd = new ContentDisposition(s);
                cd.setDisposition(disposition);
                disposition = cd.toString();
            }
            part.setHeader("Content-Disposition", disposition);
        }
    }

    static String getDescription(MimePart part)
            throws MessagingException {
        String rawvalue = part.getHeader("Content-Description", null);

        if (rawvalue == null)
            return null;

        try {
            return MimeUtility.decodeText(MimeUtility.unfold(rawvalue));
        } catch (UnsupportedEncodingException ex) {
            return rawvalue;
        }
    }

    static void
    setDescription(MimePart part, String description, String charset)
            throws MessagingException {
        if (description == null) {
            part.removeHeader("Content-Description");
            return;
        }

        try {
            part.setHeader("Content-Description", MimeUtility.fold(21,
                    MimeUtility.encodeText(description, charset, null)));
        } catch (UnsupportedEncodingException uex) {
            throw new MessagingException("Encoding error", uex);
        }
    }

    static String getFileName(MimePart part) throws MessagingException {
        String filename = null;
        String s = part.getHeader("Content-Disposition", null);

        if (s != null) {
            // Parse the header ..
            ContentDisposition cd = new ContentDisposition(s);
            filename = cd.getParameter("filename");
        }
        if (filename == null) {
            // Still no filename ? Try the "name" ContentType parameter
            s = part.getHeader("Content-Type", null);
            s = MimeUtil.cleanContentType(part, s);
            if (s != null) {
                try {
                    ContentType ct = new ContentType(s);
                    filename = ct.getParameter("name");
                } catch (ParseException pex) {
                }    // ignore it
            }
        }
        if (decodeFileName && filename != null) {
            try {
                filename = MimeUtility.decodeText(filename);
            } catch (UnsupportedEncodingException ex) {
                throw new MessagingException("Can't decode filename", ex);
            }
        }
        return filename;
    }

    static void setFileName(MimePart part, String name)
            throws MessagingException {
        if (encodeFileName && name != null) {
            try {
                name = MimeUtility.encodeText(name);
            } catch (UnsupportedEncodingException ex) {
                throw new MessagingException("Can't encode filename", ex);
            }
        }

        // Set the Content-Disposition "filename" parameter
        String s = part.getHeader("Content-Disposition", null);
        ContentDisposition cd =
                new ContentDisposition(s == null ? Part.ATTACHMENT : s);
        // ensure that the filename is encoded if necessary
        String charset = MimeUtility.getDefaultMIMECharset();
        ParameterList p = cd.getParameterList();
        if (p == null) {
            p = new ParameterList();
            cd.setParameterList(p);
        }
        if (encodeFileName)
            p.setLiteral("filename", name);
        else
            p.set("filename", name, charset);
        part.setHeader("Content-Disposition", cd.toString());

        /*
         * Also attempt to set the Content-Type "name" parameter,
         * to satisfy ancient MUAs.  XXX - This is not RFC compliant.
         */
        if (setContentTypeFileName) {
            s = part.getHeader("Content-Type", null);
            s = MimeUtil.cleanContentType(part, s);
            if (s != null) {
                try {
                    ContentType cType = new ContentType(s);
                    // ensure that the filename is encoded if necessary
                    p = cType.getParameterList();
                    if (p == null) {
                        p = new ParameterList();
                        cType.setParameterList(p);
                    }
                    if (encodeFileName)
                        p.setLiteral("name", name);
                    else
                        p.set("name", name, charset);
                    part.setHeader("Content-Type", cType.toString());
                } catch (ParseException pex) {
                }    // ignore it
            }
        }
    }

    static String[] getContentLanguage(MimePart part)
            throws MessagingException {
        String s = part.getHeader("Content-Language", null);

        if (s == null)
            return null;

        // Tokenize the header to obtain the Language-tags (skip comments)
        HeaderTokenizer h = new HeaderTokenizer(s, HeaderTokenizer.MIME);
        List<String> v = new ArrayList<>();

        HeaderTokenizer.Token tk;
        int tkType;

        while (true) {
            tk = h.next(); // get a language-tag
            tkType = tk.getType();
            if (tkType == HeaderTokenizer.Token.EOF)
                break; // done
            else if (tkType == HeaderTokenizer.Token.ATOM)
                v.add(tk.getValue());
            else // invalid token, skip it.
                continue;
        }

        if (v.isEmpty())
            return null;

        String[] language = new String[v.size()];
        v.toArray(language);
        return language;
    }

    static void setContentLanguage(MimePart part, String[] languages)
            throws MessagingException {
        StringBuilder sb = new StringBuilder(languages[0]);
        int len = "Content-Language".length() + 2 + languages[0].length();
        for (int i = 1; i < languages.length; i++) {
            sb.append(',');
            len++;
            if (len > 76) {
                sb.append("\r\n\t");
                len = 8;
            }
            sb.append(languages[i]);
            len += languages[i].length();
        }
        part.setHeader("Content-Language", sb.toString());
    }

    static String getEncoding(MimePart part) throws MessagingException {
        String s = part.getHeader("Content-Transfer-Encoding", null);

        if (s == null)
            return null;

        s = s.trim();    // get rid of trailing spaces
        if (s.length() == 0)
            return null;
        // quick check for known values to avoid unnecessary use
        // of tokenizer.
        if (s.equalsIgnoreCase(EncoderTypes.BIT7_ENCODER.getEncoder()) || s.equalsIgnoreCase(EncoderTypes.BIT8_ENCODER.getEncoder()) ||
                s.equalsIgnoreCase(EncoderTypes.QUOTED_PRINTABLE_ENCODER.getEncoder()) ||
                s.equalsIgnoreCase(EncoderTypes.BINARY_ENCODER.getEncoder()) ||
                s.equalsIgnoreCase(EncoderTypes.BASE_64.getEncoder()))
            return s;

        // Tokenize the header to obtain the encoding (skip comments)
        HeaderTokenizer h = new HeaderTokenizer(s, HeaderTokenizer.MIME);

        HeaderTokenizer.Token tk;
        int tkType;

        for (; ; ) {
            tk = h.next(); // get a token
            tkType = tk.getType();
            if (tkType == HeaderTokenizer.Token.EOF)
                break; // done
            else if (tkType == HeaderTokenizer.Token.ATOM)
                return tk.getValue();
            else // invalid token, skip it.
                continue;
        }
        return s;
    }

    static void setEncoding(MimePart part, String encoding)
            throws MessagingException {
        part.setHeader("Content-Transfer-Encoding", encoding);
    }

    /**
     * Restrict the encoding to values allowed for the
     * Content-Type of the specified MimePart.  Returns
     * either the original encoding or null.
     */
    static String restrictEncoding(MimePart part, String encoding)
            throws MessagingException {
        if (!ignoreMultipartEncoding || encoding == null)
            return encoding;

        if (encoding.equalsIgnoreCase(EncoderTypes.BIT7_ENCODER.getEncoder()) ||
                encoding.equalsIgnoreCase(EncoderTypes.BIT8_ENCODER.getEncoder()) ||
                encoding.equalsIgnoreCase(EncoderTypes.BINARY_ENCODER.getEncoder()))
            return encoding;    // these encodings are always valid

        String type = part.getContentType();
        if (type == null)
            return encoding;

        try {
            /*
             * multipart and message types aren't allowed to have
             * encodings except for the three mentioned above.
             * If it's one of these types, ignore the encoding.
             */
            ContentType cType = new ContentType(type);
            if (cType.match("multipart/*"))
                return null;
            if (cType.match("message/*") &&
                    !MimeUtility.getBooleanSystemProperty(
                            "mail.mime.allowencodedmessages", false))
                return null;
        } catch (ParseException pex) {
            // ignore it
        }
        return encoding;
    }

    static void updateHeaders(MimePart part) throws MessagingException {
        DataHandler dh = part.getDataHandler();
        if (dh == null) // Huh ?
            return;

        try {
            String type = dh.getContentType();
            boolean composite = false;
            boolean needCTHeader = part.getHeader("Content-Type") == null;

            ContentType cType = new ContentType(type);

            /*
             * If this is a multipart, give sub-parts a chance to
             * update their headers.  Even though the data for this
             * multipart may have come from a stream, one of the
             * sub-parts may have been updated.
             */
            if (cType.match("multipart/*")) {
                // If multipart, recurse
                composite = true;
                Object o;
                if (part instanceof MimeBodyPart) {
                    MimeBodyPart mbp = (MimeBodyPart) part;
                    o = mbp.cachedContent != null ?
                            mbp.cachedContent : dh.getContent();
                } else if (part instanceof MimeMessage) {
                    MimeMessage msg = (MimeMessage) part;
                    o = msg.cachedContent != null ?
                            msg.cachedContent : dh.getContent();
                } else
                    o = dh.getContent();
                if (o instanceof MimeMultipart)
                    ((MimeMultipart) o).updateHeaders();
                else
                    throw new MessagingException("MIME part of type \"" +
                            type + "\" contains object of type " +
                            o.getClass().getName() + " instead of MimeMultipart");
            } else if (cType.match("message/rfc822")) {
                composite = true;
                // XXX - call MimeMessage.updateHeaders()?
            }

            /*
             * If this is our own MimePartDataHandler, we can't update any
             * of the headers.
             *
             * If this is a MimePartDataHandler coming from another part,
             * we need to copy over the content headers from the other part.
             * Note that the MimePartDataHandler still refers to the original
             * data and the original MimePart.
             */
            if (dh instanceof MimePartDataHandler) {
                MimePartDataHandler mdh = (MimePartDataHandler) dh;
                MimePart mpart = mdh.getPart();
                if (mpart != part) {
                    if (needCTHeader)
                        part.setHeader("Content-Type", mpart.getContentType());
                    // XXX - can't change the encoding of the data from the
                    // other part without decoding and reencoding it, so
                    // we just force it to match the original, but if the
                    // original has no encoding we'll consider reencoding it
                    String enc = mpart.getEncoding();
                    if (enc != null) {
                        setEncoding(part, enc);
                        return;
                    }
                } else
                    return;
            }

            // Content-Transfer-Encoding, but only if we don't
            // already have one
            if (!composite) {    // not allowed on composite parts
                if (part.getHeader("Content-Transfer-Encoding") == null)
                    setEncoding(part, MimeUtility.getEncoding(dh));

                if (needCTHeader && setDefaultTextCharset &&
                        cType.match("text/*") &&
                        cType.getParameter("charset") == null) {
                    /*
                     * Set a default charset for text parts.
                     * We really should examine the data to determine
                     * whether or not it's all ASCII, but that's too
                     * expensive so we make an assumption:  If we
                     * chose 7bit encoding for this data, it's probably
                     * ASCII.  (MimeUtility.getEncoding will choose
                     * 7bit only in this case, but someone might've
                     * set the Content-Transfer-Encoding header manually.)
                     */
                    String charset;
                    String enc = part.getEncoding();
                    if (enc != null && enc.equalsIgnoreCase(EncoderTypes.BIT7_ENCODER.getEncoder()))
                        charset = "us-ascii";
                    else
                        charset = MimeUtility.getDefaultMIMECharset();
                    cType.setParameter("charset", charset);
                    type = cType.toString();
                }
            }

            // Now, let's update our own headers ...

            // Content-type, but only if we don't already have one
            if (needCTHeader) {
                /*
                 * Pull out "filename" from Content-Disposition, and
                 * use that to set the "name" parameter. This is to
                 * satisfy older MUAs (DtMail, Roam and probably
                 * a bunch of others).
                 */
                if (setContentTypeFileName) {
                    String s = part.getHeader("Content-Disposition", null);
                    if (s != null) {
                        // Parse the header ..
                        ContentDisposition cd = new ContentDisposition(s);
                        String filename = cd.getParameter("filename");
                        if (filename != null) {
                            ParameterList p = cType.getParameterList();
                            if (p == null) {
                                p = new ParameterList();
                                cType.setParameterList(p);
                            }
                            if (encodeFileName)
                                p.setLiteral("name",
                                        MimeUtility.encodeText(filename));
                            else
                                p.set("name", filename,
                                        MimeUtility.getDefaultMIMECharset());
                            type = cType.toString();
                        }
                    }
                }

                part.setHeader("Content-Type", type);
            }
        } catch (IOException ex) {
            throw new MessagingException("IOException updating headers", ex);
        }
    }

    static void invalidateContentHeaders(MimePart part)
            throws MessagingException {
        part.removeHeader("Content-Type");
        part.removeHeader("Content-Transfer-Encoding");
    }

    static void writeTo(MimePart part, OutputStream os, String[] ignoreList)
            throws IOException, MessagingException {

        // see if we already have a LOS
        LineOutputStream los = null;
        if (os instanceof LineOutputStream) {
            los = (LineOutputStream) os;
        } else {
            Map<String, Object> params = new HashMap<>();
            params.put("allowutf8", allowutf8);
            los = part.getStreamProvider().outputLineStream(os, allowutf8);
        }

        // First, write out the header
        Enumeration<String> hdrLines
                = part.getNonMatchingHeaderLines(ignoreList);
        while (hdrLines.hasMoreElements())
            los.writeln(hdrLines.nextElement());

        // The CRLF separator between header and content
        los.writeln();

        // Finally, the content. Encode if required.
        // XXX: May need to account for ESMTP ?
        InputStream is = null;
        byte[] buf = null;
        try {
            /*
             * If the data for this part comes from a stream,
             * and is already encoded,
             * just copy it to the output stream without decoding
             * and reencoding it.
             */
            DataHandler dh = part.getDataHandler();
            if (dh instanceof MimePartDataHandler) {
                MimePartDataHandler mpdh = (MimePartDataHandler) dh;
                MimePart mpart = mpdh.getPart();
                if (mpart.getEncoding() != null)
                    is = mpdh.getContentStream();
            }
            if (is != null) {
                // now copy the data to the output stream
                buf = new byte[8192];
                int len;
                while ((len = is.read(buf)) > 0)
                    os.write(buf, 0, len);
            } else {
                os = MimeUtility.encode(os,
                        restrictEncoding(part, part.getEncoding()));
                part.getDataHandler().writeTo(os);
            }
        } finally {
            if (is != null)
                is.close();
            buf = null;
        }
        os.flush(); // Needed to complete encoding
    }

    /**
     * A special DataHandler used only as a marker to indicate that
     * the source of the data is a MimePart (that is, a byte array
     * or a stream).  This prevents updateHeaders from trying to
     * change the headers for such data.  In particular, the original
     * Content-Transfer-Encoding for the data must be preserved.
     * Otherwise the data would need to be decoded and reencoded.
     */
    static class MimePartDataHandler extends DataHandler {
        MimePart part;

        public MimePartDataHandler(MimePart part) {
            super(new MimePartDataSource(part));
            this.part = part;
        }

        InputStream getContentStream() throws MessagingException {
            InputStream is = null;

            if (part instanceof MimeBodyPart) {
                MimeBodyPart mbp = (MimeBodyPart) part;
                is = mbp.getContentStream();
            } else if (part instanceof MimeMessage) {
                MimeMessage msg = (MimeMessage) part;
                is = msg.getContentStream();
            }
            return is;
        }

        MimePart getPart() {
            return part;
        }
    }
}
